Not in the sense of "wrong", but in terms of difficulty of comprehension, for me it's call/cc in scheme: http://en.wikipedia.org/wiki/Call-with-current-continu

Not in the sense of "wrong", but in terms of difficulty of comprehension, for me it's call/cc in scheme: http://en.wikipedia.org/wiki/Call-with-current-continuation http://en.wikipedia.org/wiki/Call-with-current-continuation The main thing which helped me get some kind of grip on it was having worked through longjmp/setjump in C some time ago.